Screening for diseases with molecular defects in protein C receptor

内皮细胞蛋白C受体（EPCR）能够特异性地与血浆抗凝蛋白C高亲和力结合。蛋白C作为丝氨酸蛋白酶的酶原形式循环，并且当在内皮细胞表面上转化为活性形式的酶时作为抗凝剂起作用。已发现凝血酶/血栓调节蛋白（TM）复合物介导活化的催化反应。我们发现，EPCR大大加速蛋白C激活介导的复合物，通过使用转染细胞系和功能阻断抗EPCR单克隆抗体。在生理条件下，EPCR似乎是蛋白C激活所必需的，因此，该分子的异常功能或表达可能导致血液凝固缺陷。我们发现，功能性EPCR诱导从胶质母细胞瘤和单核细胞白血病患者建立的几个细胞系。M4和M5型急性粒细胞白血病患者外周血单个核细胞（PBMC）EPCR也呈阳性，而健康人PBMC则呈阴性。EPCR可能成为某些类型癌症的新标志物，该分子的异常表达可能解释癌症中的某些凝血障碍。我们还建立了EPCR基因缺陷的筛选体系，建立了EPCR基因外显子的PCR扩增方法和直接测序方法。目前正在使用这些方法进行筛选。

The endothelial cell protein C receptor (EPCR) is capable of high-affinity binding specific for plasma anticoagulant protein C.Protein C circulates as a zymogen form of serine protease and functions as an anticoagulant when is converted to active form of enzyme on the endothelial cell surface. The thrombin/thrombomodulin (TM) complex has been found to mediate the catalytic reaction for the activation. We found that EPCR greatly accelerated protein C activation mediated by the complex by using transfected cell lines and function blocking anti-EPCR monoclonal antibodies. EPCR appears to be essential for protein C activation under the physiological conditions, therefore, abnormal function or expression of this molecule might cause defects in blood coagulation. We found that functional EPCR was induced in several cell lines established from glioblastoma and monoblastic leukemia patients. Peripheral blood mononuclear cells (PBMC) from patients with acute myerocytic leukemia type M4 and M5 were also positive for EPCR.In contrast, PBMC from healthy donors were negative for the antigen. EPCR could be a novel marker for some types of cancers, and abnormal expression of this molecule might explain some disorder of blood coagulation in cancer. We also developed a screening system to detect the genetic defects of EPCR.We established PCR methods to amplify the exons of EPCR and also established direct sequencing methods. Screening by using these methods is now under going.